There has been developed a system for remotely controlling electrical loads distributed over a wide area (such as a large office building or factory) from a microprocessor based central controller. That system is disclosed in U.S. Pat. No. 4,367,414--Miller et al, issued Jan. 4, 1983. The information disclosed in that patent is incorporated by reference thereto as if fully set forth herein. In the Miller '414 system, control instructions are issued by the central controller 50 and are transmitted to various transceiver-decoders 56 via a twisted pair cable 58 constituting a bidirectional communications channel. A particular transceiver-decoder that is "addressed" carries out the command by actuating one or more particular relays to make or break an electrical connection as desired. The central controller issues its control instructions in accordance with a predetermined schedule, in response to a measured parameter (such as light level or temperature) or in response to a user switch actuation sensed by a switch processor in the transceiver decoder and transmitted to the central controller over the bi-directional communications link, or in response to a user command telephonically transmitted to the central controller.
Although the Miller '414 system operates effectively as disclosed, further enhancements are now possible. This patent is directed to improvements in the transceiver-decoder, particularly to a relay control module for energizing remote control relays.
The enhanced transceiver-decoder is configured in a modular fashion. Separate switch and relay "modules" are provided to allow a user of the product to configure a remote control panel to meet his specific application needs. This modular construction is field adaptable allowing an electrician who has no electronic expertise to easily install, replace and service the panels. To do this, small modules are developed so that they can be easily handled and configured in the field. Therefore, a reduction in component count over the Miller '414 arrangement is achieved for driving the same amount of remote control relay loads. The response of a transceiver to relay actuation commands from the central controller is improved. The response time is increased to improve human acceptable perception of relay actuation. Furthermore, compensation for parametric shifts in relay characteristics is made to reduce the propensity for perceived failures of the remote control relay. This compensation is made in the actuating signal provided to the relay.
There is also provided improved protection circuitry to insure that faulty relays do not destroy the more expensive electronic modules. Since these remote control relays are actuated by electronic circuitry means, a short in the relay or an external wire can cause excessive current to be delivered causing a self-destruction of the electronic device. A power limiting circuit is needed which reduces this propensity and can annunciate relay faults so they can be traced and quickly replaced. Improved diagnostics is also provided to insure the integrity of the load actuation data base and speed the tracing of system faults.
There is also provided a special warning pulse sequence (flicker or warning mode operation) to warn the remote occupant that lights are about to go off. This will give the occupant time to call the computer to keep the lights on.